Thomas Klimmasch

The influence of weathering on scratches and on scratch and mar resistance of automotive coatings

Automotive coatings are expected to retain a good scratch resistance over years of service. On the other hand, scratches once arisen should disappear by reflow or should not become more visible during further use of the car. These expectations are a challenge to the paint manufacturer and are not easy to fulfil as our work will show. Seven car coatings were examined, each with different PU clearcoats. The coatings were treated under artificial weathering conditions before and after the scratch test. Scratching was carried out using laboratory car wash and Nano Scratch techniques. In comparison to other essential coating properties measured, the scratch and mar resistance was mainly affected by pre-weathering. Alterations in reflow behaviour, shape and size of single scratches were observed during post-weathering which included partly acid precipitation.